Centralized traffic controlling system for railroads



T. J. JUDGE April 25, 1939.

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 3 Sheets-Sheet 1 Filed Sept. 27, 1932 April 25, 1939. T. J. JUDGE 2,155,554

CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS Filed Sept 27, 1932 5 Sheets-Sheet 2 MON INVENTO (7.

m, ATTORNEY April 25, 1939.

T. J. JUDGE CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROADS 5' Sheets-Sheet 3 QM EX Filed Sept. 27, 1932 i lwmmwvl t oll kWN/TL meoql mac 195 b b w n u uvo 2.52. 5 u t "35 m M H- v Patented Apr. 25, 1939 PATENT OFFICE CENTRALIZED TRAFFIC CONTROLLING SYSTEM FOR RAILROAD'S Thomas J. Judge, Rochester, N. Y., assignor to General Railway Signal Company, Rochester,

Application September 27, 1932, Serial No. 635,062

40 Claims.

This invention relates to centralized traflic controlling systems for railroads and more particularly to a system whereby railroad traffic is controlled from a control office and the location of trains as well as the condition of traffic controlling devices at remote locations are indicated to an attendant at the control office. Such a system is supplemented by the well-known auto matic block signals and other local means which are ordinarily provided toprevent unsafe train movements, improper operation of track switches or the like. The system of this invention comprises a communication system extending from the control ofiice to field stations located at appropriate points in the territory under the supervision of an attendant or operator.

Such a communication system is of particular utility in enabling the operator to select and actuate a relay or control device for each switch or signal at any desired station in his territory to effect the actuation of the switches and signals to different positions at his will, subject to their automatic control which is ordinarily provided to prevent unsafe conditioning. This selection and actuation feature is conveniently referred to as transmission of controls and may be effected by a manual operation under the control of the operator. The communication system may also be used to transmit to the operator indications of the positions of switches and signals, the presence or absence of trains and such other indications as may be useful in directing and supervising train movements in various track sections. Such a function is conveniently termed transmission of indications and may be automatically effected when a new indication is to be transmitted to the control oflice either when the system is at rest or when it is being used to transmit controls from the control office.

The system of this disclosure is of the duplex coded type since the transmission of controls and the transmission of indications can occur simultaneously and since the transmission of controls and indications is by means of code impulses. This feature is so incorporated in the system that duplex or two-way transmission can simultaneously occur to and from the same station or to and from different stations.

This application is a continuation in part of my copending abandoned application Ser. No. 589,783 filed January 30, 1932.

The present invention may be considered as an improvement over the system disclosed in the prior application of N. D. Preston et al., Ser. No.

455,304, filed May 24, 1930, now Patent No.

2,129,183, dated Sept. 6, 1938. This prior application discloses a communication system of the duplex coded type providing the above-mentioned features over twocircuits extending from the control office to the field stations. The invention of the present application is directed to the transmission of controls and indications by means of a single circuit extending from the control oflice to the field stations. By effecting such selection and transmission over a two-wire circuit obvious economies in the construction and maintenance of the line are realized.

Other objects and advantages of the present invention will be hereinafter set forth in the. specification and claims and shown in the drawings. The present disclosure is intended to show only the elemental principles of the invention and in order to simplify the drawings and descriptive matter as much as possible only such portions of a complete system are'illustrated as will most clearly convey the features disclosed.

In describing the invention in detail reference will be made to the accompanying drawings which illustrate in a diagrammatic manner the apparatus and circuits as employed in accordance with the present invention. Fig. 1 illustrates the apparatus and circuits employed at the control ofiioe. Fig. 2 illustrates the apparatus and circuits employed at one of the field stations. Fig. 3 illustrates a modification showing how two or more groups may be operated at the same station by using most of the equipment in common for all groups at the same station. The two wire line circuit connecting the control office with the fieldstations is shown in the upper portion of Figs. 1 and 2 and the operation of the apparatus at the control ofiice and at the field station may be conveniently followed by placing the drawing of Fig. 2 to the right of Fig. 1.

Within the dotted rectangle in the upper central portion of Fig. 2, the extension of the two wire line circuit through other stations is indicated. It will be understood that the line circuit may extend through one or more additional field stations having apparatus and circuit arrangements practically the same as that shown in Fig. 2. As will be clearly pointed out in the following description, the points of difference in the circuit connections at diiferent field stations are the distinctive connections of the code jumpers so that a particular field station will be fully responsive only to a particular code assigned to this field station.

GENERAL DESCRIPTION No attempt has been made to show all of the apparatus, such as the total number of manual controls at the control office or the exact arrangement of the equipment at the field stations, since this arrangement may vary to suit local conditions. There may be included at the control ofiice a number of groups of manually operable devices, each group corresponding to a field station and being provided with an associated starting button. The operation of any one of these buttons puts the system through an operating cycle during which a station corresponding to the operated button will be selected.

These manually operable devices consist of switch machine levers, signal levers and the like for the purpose of controlling the various traffic devices at the selected field station. Only one lever is shown in the drawings of this application since a complete description of the operation of such levers and the signals they control is given in the above-mentioned application Ser. No. 455,304. This above-mentioned application also discloses how a plurality of controls may be stored by the operator and, how these controls may be applied to the system in proper rotation when several starting buttons are actuated simultaneously or in rapid succession.

The controls are transmitted from the control oflice over two line wires in series by means of a succession of positive and negative impulses arranged in code combinations, each particular combination of impulses being effective to select a corresponding field station. Following station selection, additional code impulses are applied to the line for positioning the switch machine relay and the signal relays for the purpose of governing the traific in the section of track associated with the selected station. The complete circuit arrangement for actuating the switch machine and signals is not shown since it is now well known how these various devices operate when their circuits are properly governed by the relays operated from the control office.

If, while transmission of controls is taking place, no indications are being transmitted, the open periods of the line circuit are of substantially equal duration and the impulses for selecting the desired station and transmitting the desired controls to the station follow each other in rapid succession.

The line relay in the control office and the line relay at the field stations are normally energized by current flowing in the line circuit from a battery in the control office. When controls or indications are to be transmitted, the line circuit is opened momentarily to initiate the operation of the system after which the stepping relays at the control office go through an operating cycle. The impulses which are connected to the line on subsequent closures are each effective to operate a stepping relay at both the control ofiice and at the field station, irrespective of the polarity of the impulses. The stepping relays at the station which will be selected go through the operating cycle in synchronism with those at the control office. The stepping relays at other stations operate during a portion of the operating cycle only, since they are dropped out at different points during the cycle as the code directs. For the transmission of controls the polarity of each impulse is effective to build up a code combination for selecting the desired station while the polarity of each impulse transmitted after the station is selected determines the controls established thereat.

Indications are transmitted from the field stations over the same line circuit by causing the deenergized or open periods between successive impulses to be either short or long. Combinations of short and long open periods between impulses are used to determine the selection of the station during transmission of indications as well as determining the indication which will be displayed after the station is selected. In accordance with the present invention, these combinations of short and long periods are produced at the field station and measured in the control ofiice.

When the control office places an impulse on the line of either polarity, it opens the line circuit at the end of the impulse. As soon as the line is opened, the field station either closes it or holds it open dependent upon the indication to be transmitted. The control office makes a test of the line by closing it. If the line tests open (due to the field station having an indication requiring a long open period) the control office immediately opens the line again and holds it open for a comparatively long interval. During this interval the field station closes the line but the line circuit is not energized because of its open condition in the ofiice. The line circuit is finally energized after the lapse of the long time interval measured by the control ofiice.

On the other hand, if the line is left closed at the field station subsequent to its being opened by the control office, then when the control office tries to close it for the next impulse it is immediately energized. In other words, the control oilice tries to close the line and if it is successful a short deenergized period is the result; but, if it is not successful until the second trial, a long deenergized period is the result.

The organization of a communication system in accordance with the present invention, as above outlined, gives a distinct advantage in that the timing of the spaces or time intervals between successive impulses applied to the line circuit at the control ofiice is determined by a single timing means located in the central oflice. The means at the several stations which cause time spaces to be prolonged may vary in their total time of effectiveness, but this is immaterial so long as their minimum time of effectiveness is sufiiciently long to initially cause the control office to delay a time space for an added period of time, as such added time is sufiicient to allow for the variations at the several stations. Thus, the total time which the line circuit is open is determined in the control ofilce instead at the several stations.

This system employs the superiority of code arrangement for dropping out all field stations except the one having a superior code when an attempt is being made to transmit indications from more than one field station at the same time.

Control ofiice apparatus.As typical of the control means located in the control ofiice and associated with each field station, a control lever SML is indicated in Fig. 1. A code determining relay CD associated with each station is used for connecting the variably connected code jumpers and the levers to the selecting circuits. A bank of station registering relays of conventional arrangement is indicated by reference characters P'I PT and PT These latter relays are operated by code signals when a station is to be selected for transmission of indications. They are positioned one at a time in accordance with the position of relay K, the latter relay being provided for the purpose of storing over from one period until the next executing period the condition which is to be used for positioning the PT relay (with suitable exponent).

The embodiment of the present invention utilizes the first three steps of the cycle for station selection on outbound cycles as well as for registering the stations on inbound cycles. A fourth step is utilized to select control and indication devices after station selection and registration. It is apparent that more than three steps may be provided to select more stations and that more than one step may be provided to select more controls and indications. A station to be registered for transmission of indications will cause the operation of one or more of the three PT relays in combination after which a station relay ST will be actuated on the fourth step. At this fourth step an indication relay such as IN may be positioned to light an indication lamp such as I.

A bank of four stepping relays IV, 2V, 3V and 4V is shown with their associated repeating or half step relay VP arranged in a manner to be energized in sequence on the open periods following the impulses in the line circuit. It is obvious that additional stepping relays would be used for selection in a system of larger size. The eight wires leading from the contracts of relay PT adjacent bracket A may be connected to additional station relays similar to ST, one for each station, thus indicating that eight code combinations are possible. By providing one more stepping relay for station selection it is obvious that another PT relay could be added, thus doubling the number of available stations by further pyramiding the contacts of the PT relays.

A code sending relay CS provides for selecting the polarity of the battery to be applied to the line in accordance with the code impulses required when transmitting controls. Relay K is provided for selecting the polarity of the battery to be applied to the PT relays for registering a station as well as applying this battery to the polar indicating relays IN for positioning them properly to display the required indications.

Slow operating and slow releasing cycle demarcating relays SA and SAP are provided to define the bounds of an operating cycle and to insure synchronism of the system at the beginning of each cycle. Relay C is used both as a cycle control relay and for checking the particular deenergized condition which exists as each step. This relay operates to start the cycle of operations as well as to register whether the open or deenergized condition of the line between impulses is long or short.

A three position, polarized, biased-to-neutral, line relay F is connected in the line circuit and is normally energized by current which is normally applied to the line. Relay FF is the line repeating relay and it follows the operation of relay F, that is, relay FF is energized when relay F is in either one of its actuated positions and is deenergized when relay F is in its neutral position.

Impulsing relay PL is provided for opening the line circuit at the control office. This relay is controlled by impulse marking relay E- associated with the stepping relay bank, relay E being used to mark ofi the steps for energizing relay PL at the proper time. J and JP are quick operating and slow releasing relays used to prolong the de-energized period between impulses in the line circuit when the indication requires it. EB is an auxiliary relay used to prepare the circuit for operating relay C to register the requirement for a long open period.

Field station apparatus.The traific controlling devices located at the field stations may vary according to local conditions and for example, may comprise two-position polarized'relays similar to SMR actuated to the proper position for controlling the signals. Track relay T and other relays such as relay WP record different conditions requiring transmission to the control oifice.

At each field station a line relay F and a line repeating relay FP are provided and operate in a manner similar to corresponding relays in the control oifice for governing the operation of the cycle demarcating relays SA and SAP. The F and FF relays also control the fast operating, slow releasing relay J and other circuits as will be described in detail. Two station selecting relays SO and SI are provided. S0 is the relay used to select the particular station for outbound signals or transmission of controls and SI is used to select a particular station for inbound signals or transmission of indications. An auxiliary station selecting relay SOS is provided for a purpose which will be described in detail. The stepping relay bank including the four stepping relays and the half step relay comprises an arrangement similar to that used in the control ofiice, these relays being identified by reference characters corresponding to like relays in the control office, but with the exponent (1) added. Like the stepping relays in the control ofilce they are actuated on the open period of the line circuit between impulses.

A change relay CH is indicated but its complete control circuit is not shown. It will be understood that additional relays and contacts are connected in a manner similar to the contacts of relay T and Wired in a series circuit so that any change in condition causing one of these contacts to switch from front to back will momentarily open the stick circuit of relay CH and allow it to release. The complete circuit arrangement for this CH relay may be similar to that disclosed in the patent to DeLong et. al., 1,852,402, and to simplify the present disclosure this circuit will not be shown or described in detail.

The equipment at each field station, as well as that in the control office, such as groups of associated relays, may be grouped into suitable cabinets and arranged for ease in removal for replacements or testing purposes. Various other devices and apparatus which are necessary in railway signalling practice such as terminal blocks and connections, and lightning protective equipment may also be provided but have not been indicated in this disclosure.

DETAILED OPERATION With the communication part of the centralized trafiic controlling system with which this invention is concerned at rest, all of the relays in the control ofiice are in their normal or deenergized positions except relays F, FP, J and JP. Relay F is normally positioned to the left by current flowing from the terminal of battery B, back contact I of relay CS, upper line conductor, through the normally closed back contacts similar to I02 of the PL relays at all the field stations in series, windings of all the F relays at the field stations, including the winding of relay F over the lower side of the line, back to the control office, through back contact 3 of relay PL in the control office, winding of relay F and back contact 4 of relay CS to the terminal of battery B.

With relay F positioned to the left, a circuit is closed for energizing relay FP extending from contact of relay F and winding of relay FP, to Relay J is normally energized over a circuit extending from. front contact 6 of relay FF and winding of J, to Relay JP is normally energized over a circuit extending from front contact 1 of relay J and winding of JP, to A circuit in multiple with contact 1 is completed by front contact 8 of relay FP for energizing JP, this circuit arrangement for energizing J and JP at front contacts of relay FP and for establishing an additional energizing circuit for JP at a frontcontact of J, being for the purpose of quickly actuating both of these relays simultaneously and for deenergizing them in sequence for providing a long time interval upon release.

The current in the above traced circuit, extending through relay F at the field station, positions this relay to the left and it in turn completes a circuit for energizing J extending from contact I05 of relay F back contact I06 of relay SAP and winding of J to It will thus be seen that relays F and J at the field station shown in Fig. 2 are normally energized. Likewise, the line relays such as F as well as relays similar to J at other field stations are energized when the system is at rest.

The track relay T is energized when no train is upon the detector track section. This circuit arrangement of relay T is not shown in detail, since it is now well known how it may be connected to the track for indicating the presence or absence of traffic thereon.

The system is initiated into a cycle of operations by momentarily opening the line circuit, either at the control ofiice or at any field station by means later described. A cycle consists of a definite number of impulses connected to the line at the control office and during this cycle, controls may be transmitted from the control office to select any one of the field stations and to position the controlling devices at the field stations. Indications may also be transmitted from any field station to the control oflice during this cycle. If the cycle of operations is initiated at the control office a CD relay will be actuated by the operation of an associated starting button SB. The complete operating circuits for the CD relays have been omitted for the sake of simplifying the drawings but, as has been mentioned, only one CD relay can be picked up at one time. After a cycle has been started by indications being sent in from a field station, no CD relay in the control office can be picked up until the end of this cycle. This operation of the CD relays may be similar to the arrangement disclosed in the above mentioned application, Ser. No. 455,- 304.

The short oblique connections to all the wires attached to contacts at the right of the CD relay, as well as any other wires having this indication, means that these are common connections. There are several CD relays, one for each station and the common wires shown connected to the contacts of the CD relay illustrated in Fig. 1 also connect to the corresponding contacts of other CD relays which are not shown. Those wires without this indication lead to jumpers, contacts or the like which are individual to the relay.

For convenience in describing the operation of the system, an operating cycle is divided into the following periods: 1st, line closed, normal; 2nd, line open, start; 3rd, line closed, preliminary impulse; 4th, line open, first stepping relay picked up, first indication code registration; 5th, line closed, first control code registration; 6th, line open, second stepping relay picked up, second indication code registration; 7th, line closed, second control code registration; 8th, line open, third stepping relay picked up, thirdv indication code registration; 9th, line closed, third control code registration; 10th, line open, fourth stepping relay picked up, fourth indication code registration; 11th, line closed, fourth control code registration.

sinned that the system is at rest or in its normal period and that the operator desires to transmit controls to the field station indicated in Fig. 2. This field station is selected by an outbound code combination as indicated by the code jumper connections I38, I45 and I49 associated with the two upper sets of contacts of the stepping relay bank. The particular CD relay illustrated in Fig. 1 applies this code com-v bination to the system, as indicated by code jumper connections 55 and 56 connected to contacts of the CD relay. After the switch machine lever SML and signal levers (not shown) are positioned, starting button SB, associated with the desired station, is actuated to close a front contact l3, back contact IA of relay SAP and upper winding of relay C, to It may be noted here that, since the wires attached to contact springs [3 are indicated as being common, the operation of any CD relay inthe group closes this circuit for operating the C relay, which is effective to start the cycle of operations. Relay C is picked up and stuck up over a circuit extending from front contact I5 of relay JP, front contact iii of relay C and lower winding of relay C, to The operation of the C relay closes a circuit for operating relay PL extending from front contact I! of relay C and Winding of PL, to Relay PL closes a circuit for operating relay EB extending from front contact 18 of relay PL and Winding of relay EB, to Relay EB has no function in connection with transmission of controls and its purpose will be described in connection with transmission of indications. The operation of relay PL opens, at its back contact 3, the line circuit which carries the operation into the start period and releases relay F in the control office, relay F at the station indicated in Fig. 2 and other relays similar to F at all field stations.

The release of relay F in the control office opens the circuit of relay FP allowing the latter relay to release, while the release of relay F at the field station closes a circuit for energizing relay SA extending from back contact ID! of This 20 "Iransmisszon of controls Mona-It will be as-' relay SAP contact I08 of relay F and winding of relay SA to The operation of relay SA closes a circuit for operating relay SAP extending from front contact I09 of relay SA and winding of relay SAP to When relay SA operates and before the operation of relay SAP a circuit is closed for operating relay SO extending from front contact III of relay SA back contact II2 of relay SAP and lower winding of relay S0, to Relay SO completes a stick circuit for itself extending from front contact III of relay SA back contact H3 of relay FP front contact II4 of relay SO and upper winding of relay S0, to It will be understood that this series of operations occurs at all field stations so that at this time all SO relays are energized.

In the control office the release of relay FP closes a circuit for actuating relay SA extending from back contact 2I of relay FP, back contact 22 of relay SAP and winding of relay SA, to A substitute circuit around contact 22 is established by contact 23 of the SA relay while it is energized. A circuit is now completed for actuating relay SAP extending from front contact 24 of relay SA and winding of relay SAP, to

A circuit is completed at this time for operating relay CS extending from front contact 25 of relay CD, back contacts 26, 21, 28 and 29 in series of the four stepping relays, front contact 3| of relay SAP and lower winding of relay CS, to Since contact 25 is connected in multiple to all CD relays, the operation of any one of these relays establishes the circuit for energizing relay CS. The operation of the CS relay reverses the battery connected to the line circuit by switching contacts I and 4. At this time however, the line circuit is open so this has no effect on the F relays.

The first open period of the line is of comparatively long duration and is used to start the cycle of operations. This long time interval is obtained by releasing the J and JP relays in sequence. When the FP relay was released as above described, the circuit which normally held relay J energized was opened at front contact 6 of relay FP. After a predetermined time interval, relay J drops and at its front contact I opens the energizing circuit of relay JP, and after an additional predetermined period of time, relay JP is released. The release of relay JP closes a circuit for operating relay K extending from back contact I5 of relay JP and lower winding of relay K, to The release of relay JP also opens at its front contact I5, the stick circuit of relay C, allowing this latter relay to drop. When relay drops, it opens at its front contact H, the circuit of relay PL, this latter relay is de-energized and the line circuit in the control office is closed for the preliminary impulse period.

Again referring to the field station circuit, the restoring of relay F to its neutral position by opening the line circuit as above described, opens at contact I the energizing circuit of relay J allowing this latter relay to deenergize after an interval of time substantially the same as the time required for releasing relay J in the control oflice. It will be noted however, that relay J will be released before relay JP is released.

The above operations at the control ofiice and at the field stations have been effective to start the cycle of operations by opening the line in the control oflice, conditioning certain relays and again closing the line in the control oflice. The

line is energized at the time the control oflice makes the preliminary impulse closure due to relays PL PL etc., at the stations being deenergized. This is because no indications are to'be transmitted at this time.

The line circuit being now energized, again picks up relay F in the control office, and over a circuit extending through contact I9 of relay F, relay FF is again actuated. The release of relay PL, above described, also opened the circuit of relay EB allowing this latter relay to drop away. Relay F is actuated to its right hand position, because relay CS is energized, and reverses the current flow over the line conductors, causing this current to be in the opposite direction from normal. This impulse is made at the start of each control or duplex cycle irrespective of the code combination associated with the desired station, for the purpose of energizing the SOS relay at the station and maintaining its associated SO relay in its energized condition at this time. It will be understood that one-half of the code combinations used for selecting stations will begin with therefore, it is necessary to provide a preliminary to condition the SOS relay before the first code impulse is applied to the line.

The energized line circuit is also effective to again energize relay F and this relay closes a circuit from its contact II5, front contact I06 of relay SAP front contact H6 of relay SO and winding of relay FP' to Relay F closes a circuit for operating SOS extending from front contact III of relay SO, contact IIB of relay F now in its right hand position, back contacts II9, I 28, I2I and I22 of the four stepping relays in series, lower winding of relay SOS and lower winding of relay S0, to also maintains relay SO in its actuated position and the operation of relay SOS establishes an additional circuit to stick the SO relay, extending from front contact I23 of relay SOS, front contact II4 of relay SO and upper winding of relay S0, to Relay SOS is also stuck up through its upper winding and its front contact I31, front contact I I3 of relay FP and front contact III of relay SA to Again referring to the control office circuit, the actuation of relay FP closes a circuit for operating relay J and this relay in turn establishes the circuit for energizing relay JP, as has already been described. From this point on until the start of another cycle the impulses follow each other in rapid succession and the open periods between impulses are of short duration so that the J and JP relays do not drop away. The closed periods are also short so that relays SA and SAP do not release. The operation of relay FP establishes a stick circuit for relay K extending from front contact 32 of relay SAP, front contact 33 of relay FP, front contact 34 of relay K and upper winding of relay K, to

This circuit Relay FP also closes an energizing circuit for the VP relay extending from front contact 35 of relay SAP, front contact 36 of relay FP, back contact 31 of relay IV, and winding of relay VP, to Relay VP establishes a substitute branch of the above described circuit, from contact 35 of relay SAP and front contact 38 of relay VP, over the remainder of the above described circuit, to the winding of VP. This substitute circuit is for the purpose of maintaining VP in its energized position, irrespective of the operation of PP, as long as relay IV is de-energized.

Again referring to the field station, the actuation of relay FP above described, closes a circuit for actuating relay J extending from front front contact I25 of relay SAP front contact I26 of relay FP back contact 21 of relay I V and winding of relay VP to Relay VP is likewise held energized over a branch circuit extending through contact I28 of relay VP in order that this relay will remain actuated irrespective of the switching over of contacts I26 of relay FP as long as the first stepping relay IV is de-energized.

Referring back to the control office, the actuation of relay VP closes a circuit for operating relay E extending from back contacts M, 42, 43 and 44 of the four stepping relays in series, lower winding of relay E and front contact 45 of relay VP, to Relay E closes an operating circuit for relay EB extending from front contact 39 of relay E and winding'of relay EB, to Relay E. also closes an operating circuit for relay PL extending from front contact 46 of relay E and winding of relay PL, to

This actuation of relay PL opens at its contact 3, the line in the control office, allowing relays F and FF to be released. This is the period during which the first stepping relay is picked up. Relays F1 and F1 at the station are likewise released. The release of relay FP in the control oflice closes a circuit which picks up the first stepping relay IV, extending from front contact 32 of relay SAP, back contact 33 of relay FP, front contact 41 of relay VP, back contact 48 of relay 4V, back contact 49 of relay 2V and winding of relay IV, to Relay IV is stuck up until the end of the cycle through its own front contact 5I, stick conductor 2 and front contact 52 of relay SAP, to Relay VP is now maintained in its energized condition over a circuit extending from front contact 35 of relay SAP, back contact 36 of relay FP, front contact 53 of relay VP and winding of this relay, to

Relay IV at the station is actuated at substantially the same time as relay IV in the office, over a circuit extending from front contact I25 of relay SAP back contact I29 of relay FP front contact I3I of relay SO, front contact I32 of relay VP back contact I33 of relay 4V back contact I 34 of relay 2V and winding of relay I V to Relay IV is stuck up until the end of the cycle over a circuit extending from front contact I25 of relay SAP stick conductor I33 and front contact I35 of relay IV Relay VP is now held in its energized condition over a circuit extending from front contact I25 of relay SAP back contact I26 of relay FP front contact I36 of relay VP and winding of this relay to The operation of relay IV opens the original operating circuit of relay SOS at back contact I 22 of IV Since relay FP is now down, the stick circuit through contact I31 of relay SOS is broken and this relay drops. Relay S0 is stuck up at this time through its front contact I I4, back contact II3 of relay PP and front contact III of relay SA to Referring back to the control ofiice, the dropping of relay FP opens the stick circuit of relay K and this latter relay de-energizes. The picking up of the IV relay opens the circuit of relay E at back contact 44 of relay IV allowing relay E to drop and it in turn allows the PL and EB relays to release.

The release of relay PL again closes the line circuit at its contact 3 for the first control code 15 period and relays F and FF are again-picked up over the circuits above described, the circuit of relay FP being closed at contact I9 of relay F because relay CS is up for a reason which will now be explained. The previously traced circuit for picking up the CS relay through back contact 26 of relay IV is broken when relay IV is operated. Relay CS may be de-energized momentarily but will be immediately picked up over a circuit extending through front contact 26 of relay IV, front contact 54 of relay CD and code jumper 55, to This circuit will be effective to get relay CS up before relay PL drops and closes the line circuit at its contact 3, thus connecting battery B to the line in such a direction that relays F and F are positioned to the right.

Jumper 55 is connected to complete the circuit of front contact 54 of relay CD to since the first impulse is because the assumed desired station has a code combination Code jumper 56 is likewise connected since the second impulse is assumed to be but the code jumper associated with front contact 51 of relay CD is not connected, since the third impulse is assumed to be Therefore, relay CS will be up on the second step and down on the third step. It will be evident that if the first impulse of the code corresponding to a desired station is to be jumper 55 is omitted and if the second impulse is jumper 55 is omitted from the connections leading to the contacts of the CD relay corresponding to such station.

The closure of the line circuit for the first code impulse also picks up relays F and FP at the station and since this is a impulse, relay F will operate to the right closing its contact I I5 for operating relay FP Relay SOS will be energized at this time over a circuit extending from front contact II! of relay SO, contact II8 of relay 5, back contacts II9, I20 and I2I of relays 4V 3V and 2V in series, front contact I22 of relay IV code jumper I38, control bus I53 and lower windings of relays SOS and SO in series to Code jumper I38 is connected to bus I53 at all stations having a code combination beginning with At all stations beginning with this jump-er is omitted, so that at this time, at these latter stations the SOS relays are not picked up and since the FP relays are picked up there are no circuits for holding the SO relays at these stations and they release. When an S0 relay de-energizes after the start of a cycle, it cannot again be pick-ed up until another cycle starts since its only pick-up circuit is through back contact II2 of relay SAP and this latter relay is down only after a cycle of operation has been completed. It will thus be seen that all stations which were started through the cycle with their SO relays picked up but which do not have a jumper I38, are dropped out at this time and that the SO relays, at front contacts similar to H6, open the circuits of relays similar to FP Front contacts similar to I3I of the SO relays interrupt the circuits of the stepping relays, so that these relays do not go through any further operations during this cycle at stations dropped out.

The actuation of relay SOS above described completes at its front contact I23 a stick circuit for the SO relay. A stick circuit for the SOS relay is established at its front contact I3'I by way of front contact II3 of relay PP and front contact III of relay SA to At the control office, the actuation of the FP relay opens, at its back contact 35, the stick circuit of the VP relay, allowing this latter relay to release. The VP relay at the station is likewise dropped at this time due to the fact that relay FP opens, at its back contact I26, the stick circuit of relay VP The dropping of the VP relay in the ofiice closes a circuit for again actuating relay. E, extending from back contacts 4i,

cuits above described for energizing the PL and EB relays.

Relay PL opens the line circuit at its back contact 3, allowing the F and PP relays in the control oflice and the F and FP relays at the staition to release, in a manner previously described.

This is the period during which the second step- I ping relay is picked up. The release of relay FP establishes a circuit which operates relay 2V extending from front contact 32 of relay SAP,

:Zback contact 33 of relay FP, back contact 41 of relay VP, back contact 58 of relay 3V, front contact 59 of relay IV and winding of relay 2V, to Relay 2V establishes an obvious stick circuit for itself at its front contact 6|, to on i stick conductor 2.

itself at its front contact I42, to on stick conductor I63.

When relay F restores to its neutral position it opens, at its contact II8, the circuit through the lower winding of relay SOS and the release of relay FP opens, at its front contact I I3, the stick circuit of relay SOS so that this relay is de-energized at this time. Relay SO remains in its operated position, due to its stick circuit now beng completed through back contact II3 of relay FP V Again referring to the control oflice circuit and recalling that the first two stepping relays IV and 2V are actuated and that the polarity of the second impulse is due to the fact that code jumper 56 is connected, it will be apparent that relay CS will be actuated at this time, over a circuit previously described, except that it now includes front contact 21 of relay 2V, front contact 62 of relay CD and the connected code jumper 56, to

The actuation of the 2V relay opens the circuit through the upper winding of relay E, at back ztration period so that current from battery B is effective to again pick up the F and F relays. These relays again energize the FF and FP relays by means of circuits above described. It will be obvious that the F and F relays are positioned to the right since relay CS is actuated, allowing current to flow from the side of battery B, over the lower line conductor, by way of front contact 4 of relay CS, returning to the side of this battery by way of front contact I of relay CS.

Relay VP is now actuated over a circuit extending from front contact 35 of relay SAP, front contact 36 of relay FP, back contact 63 of relay 3V, front contact 64 of relay 2V and winding of relay VP, to Relay 'VP is stuck up over a circuit independent of the FP relay contact 36, by way of front contact 38 of relay VP, over the remainder of the circuit just described.

At the station, relay VP is now actuated over a circuit extending from front contact I25 of relay SAP front contact I26 of relay FP back contact I43 of relay 3V front contact I44 of relay 2V and winding of relay VP to A substitute circuit for relay V'P independent of the FP relay contacts is established by way of front contact I28 of relay VP and over the remainder of the circuit just described. Relay SOS is now operated over a circuit extending from front contact II'I of relay SO, contact II8 of relay F back contacts H9 and I20 of relays 4V and 3V in series, front contact I2I of relay 2V code jumper I45, bus I53, lower winding of relay SOS and lower winding of relay S0, to Relay SOS establishes a stick circuit for itself at its front contact I31 and it also establishes at its front contact I23, a stick circuit for the SO relay, both circuits being previously traced.

Relay E in the control office is now picked up due to the closure of its energizing circuit extending from back contacts 4| and 42 of relays 4V and 3V, front contact 43 of relay 2V, lower winding of relay E and front contact 45 of relay VP, to The actuation of the E relay again closes circuits for actuating the EB and PL relays, the latter being effective to again open the line circuit. This is the period during which the third stepping relay is picked up. Relays F and FF in the control office and relays F and FP at the station now release. At the control office the third stepping relay 3V is actuated, over a circuit extending through back contact 33 of relay FP, front contact 41 of relay VP, back contact 48 of relay 4V and front contact 49 of relay 2V to the winding of relay 3V. This relay establishes an obvious stick circuit for itself to on stick conductor 2. Relay VP is maintained in its energized condition at this time due to the extension of through back contact 36 of relay FF and front contact 53 of relay VP to its winding.

The third stepping relay at the station is also actuated at this time over a circuit extending through back contact I29 of relay FP front contact I3I of relay SO, front contact I32 of relay VP back contact I33 of relay 4V and front contact I34.of relay 2V to the winding of 3V This third stepping relay completes a stick circuit for itself to which is connected to the common-conductor I03, used for sticking all these stepping relays. Relay VP is now maintained in its energized condition due to the connection of by way of back contact I26 of relay FP and front contact I36 of relay VP to its winding. Relay SOS is now dropped because the circuit through its lower winding is open at back contact I20 of relay 3V and because the circuit through its upper winding is open at front contact II3 of relay FP The S relay is stuck up at this time through the back contact I I 3 of relay FP over the remainder of the circuit previously described.

Referring to the control omce, relay CS is down at this time due to the fact that the circuit through front contact 28 of relay 3V to front contact of the CD relay is incomplete, since there is no code jumper connection to contact 51. This is due to the fact that the third code impulse is which requires relay CS being in its normal or de-energized condition. This connects battery B to the line conductors in the original direction, which will be effective to position relays F and F to the left when the line circuit is next closed. Relay E is released at this time because the circuit through its lower winding is broken at back contact 42 of relay 3V. The release of relay E again allows the EB and PL relays to drop, the latter relay closing the line circuit for the third impulse, the code for this impulse being assumed This is the third control code registration period.

Relays F in the control office and F at the station are now positioned to the left closing circuits for operating associated relays FP and FP Relay VP in the control oiiice is now restored to normal due to opening its stick circuit at back contact 36 of relay FP. Relay VP at the station is likewise released due to opening its stick circuit at back contact I26 of FP A circuit is now established for picking up relay SOS ex- I tending from front contact II! of relay SO,

:tion for completing the circuit to contact I46 of relay F back contact I4'I of relay 4V front contact I48 of relay 3V code jumper I49, bus I53 and lower windings of relays SOS and SO in series, to This circuit, in addition to actuating relay SOS, holds the SO relay -;until relay SOS completes, at its front contact I23, the stick circuit for relay SO. Relay SO again completes its stick circuit, as above described. Relay E in the control ofiice is now actuated over a circuit extending from. back ircontact M of relay 4V, front contact 42 of relay 3V, upper winding of relay E and back contact 45 of relay VP, to The circuits for again actuating relays PL and EB are now completed at front contacts of the E relay, the opening of :contact 3 of the PL relay opening the line cirwit and releasing relays F, FP, F and FP This is the period during which the fourth stepping relay is picked up. The actuating circuit for the stepping relays, above described, is now extended to relay 4V in the control oflice, by

way of back contact 41 of the VP relay and front contact 58 of the 3V relay. Relay 4V operates and completes a stick circuit for itself including stick conductor 2. Relay 4V at the station is actuated at this time by way of back contact I29 of relay FP front contact I3I of relay SO, back contact I32 of relay VP front contact I39 of relay 3V and winding of relay 4V to This latter relay is stuck up over stick conductor I03. Relay SOS at the station is now released, due to the above described operating circuit for this relay being opened at back contact I41 of relay 4V and its stick circuit being incomplete at front contact I I3 of relay FP Relay SO remains stuck up however, through back contact II 3 of relay F'P The CS relay in the control ofiice is now actuated if the control to be transmitted, such as switch machine lever SML, is in the proper posi- If this condition exists, then battery B is connected to the line conductors in reverse order from the normal connection, so that relay F will be positioned to the right upon the next closure of the line. It is evident that an incomplete circuit for relay CS at this time results in, what may be conveniently termed a impulse being applied to the line for positioning relay F to the left.

The energization of the 4V relay in the control 'oflice results in releasing relay E due to opening its energizing circuit at back contact M of relay 4V. This results in dropping the EB and PL re- VP and VP relays are picked up over circuits completed at front contact 65 of relay 4V in the ofiice and front contact I5I of relay 4V at the station, respectively. These relays again close their stick circuits by way of their front contacts 38 and I28 respectively.

Relay S0 at the station has its stick circuit now complete at front contact I52 of relay 4V It should be understood that the location of this contact I52 may be varied to suit conditions, for example, if only two steps are used for selecting the station, then this contact would be placed on relay 3V while if six steps were used to select the station, then this contact would be used on the next succeeding stepping relay, which would be the 1V relay. This stick circuit for relay S0 is for the purpose of holding it in its operated condition after the station has been selected and during the transmission of controls to the selected station.

Referring back to the control ofiice, the operating and stick circuits for relay VP have been described for the fourth control registration period. It will be understood how these circuits for the VP relay are extended so that the operation of this half step relay can be continued when additional stepping relays, such for example, as a 5V, 6V etc., are provided. It will be noted that when the last stepping relay is picked up there is no energizing circuit for relay E, therefore relays EB and PL are not again operated and the line circuit remains closed for a comparatively long period. It is obvious that additional stepping relays may be arranged to connect to additional control circuits, similar to the circuit leading to lever SML and these connections may be made on successive steps. This extension of the stepping relay operation has not been shown in order that the disclosure may remain as simple as possible.

Back contact 9 may be placed on the last stepping relay of the series and this stepping relay may be in addition to the number required to select the desired controls. In this way, relay CD remains in its operated position and maintains the control circuits through its make contacts complete, until after the final step is taken, after all controls have been transmitted. It will be understood that back contact 9 may be placed on stepping relay No. 7 if six stepping relays are provided for station selecting and for transmission of controls. It is also evident that a similar additional stepping relay would be provided at the station to insure synchronism of the system.

From the above description, it will be obvious that only one station will have the combination of code jumpers shown in Fig. 2 and this station will be the one that will be responsive to the combination of code jumpers indicated in Fig. 1, when the indicated CD relay is actuated. On the first step when relays similar to IV at the stations pick up, only the SO relays at stations having a code jumper arrangement which corresponds to the code jumper arrangement associated with the first step in the control office, will be maintained energized. Other SO relays will be dropped at this step. Likewise on the second step there must be a code jumper I45 at a station in order to maintain the SO relay, since the impulse is positive as determined by code jumper 56 in the control office. Those stations not having this combination will be dropped out. Those stations not having a code jumper on the third step corresponding to I49 will be dropped out when this impulse is negative. If a code jumper is connected from front contact I20 of relay 3V to bus I53, then it requires a positive impulse to hold the SO relay.

Assuming that eight combinations maybe obtained with three steps, it will thus be seen that on the first step the SO relays at one-half of the stations will be released and those stations are the ones where the first stepping relay jumper connection does not correspond to the impulse predetermined by the jumper connection of the first stepping relay in the control ofiice. Likewise, on the second step one-half of the remaining stations will be dropped out and those dropped will be those whose jumper connections are not in correspondence with the connection at the control oflice at this step. On the third step only one SO relay will be maintained energized and this will be the one corresponding to the desired station as determined by the complete code combination.

After station selection the operation of additional stepping relays such as 4V at the station, connect over the circuit through contacts I I8 and I46 of relay F by way of front contacts H9 and I4! of relay 4V to control relays such as SMR. The positioning of these polar relays SMR depends on the polarity of the impulse placed on the line. For'example, if switch lever SML in the control office is positioned to make contact with then relay CS will be actuated, which will cause relay F to be positioned to the right. This completes the circuit through the upper winding of relay SMR which may be assumed to position this relay to the right. If lever SML is in its alternate position, then relay CS Will not be energized, relay F will be actuated to the left and relay SMR will be energized through its lower winding, which may position this latter relay to the left. Relay SMR may be the relay which positions the switch machine and it will be understood that additional relays similar to SMR, when provided, connect to front contacts of additional stepping relays to'make available more controls. When these relays such as relay SMR are positioned, circuits (not shown but indicated by dotted lines I54 and I55) are completed for operating switch machine or signal devices. These circuits may be similar to those disclosed in the prior patent of S. N. Wight, Patent No. 1,889,457, dated November 29, 1932. The arrows associated with relay SMR indicate that its windings are in opposite directions, so that current through one winding will position its contacts in the opposite position from that by current in the other winding.

From the above it will be seen that after a cycle of operations has been completed, the line circuit is energized, which is effective to condition relay F in the control office to close contact 5 for maintaining relay FP energized. Likewise relays F and FP at the station will be energized. After a short time interval relay SA is released due to its circuit being opened at back contact 2! of relay FP. After an additional short time interval relay SAP is restored to normal, due to its circuit being opened at front contact 24 of relay SA. The release of relay SAP removes from all the stick circuits, which allows the stepping relays in the control ofiice to deenergize. Similar operations are effective at the field station, since relay SA has its energizing circuit opened at contact I08 of relay F and after it releases it interrupts the energizing circuit of relay SAP at front contact I09. At the station however, relay FP is restored to normal when relay SAP breaks its circuit at front-contact I06. Relay S0 is dropped due to its stick circuit being opened at front contact III of relay SA and at contact I52 of relay 4V The release of relay SO interrupts, at its front contact In, the circuit which actuated any of the control relays, such as SMR and the opening of front contact I25 of relay SAP allows the stepping relays to be restored to normal. The system may now be considered in a position of rest or its normal period.

Before proceeding with the description relating to transmission of indications, certain details of operation will be mentioned. Referring back to the portion of the description where the line circuit was first opened to initiate the cycle of operations, it will be remembered that relay K of Fig. 1 was energized and remained in its operated position until the succeeding closure of the line, at the time the preliminary impulse was applied. On the next succeeding opening of the line circuit the release of relay FP opened the stick circuit for the K relay and it was dropped. Relay K has no function at this time since it is only used in connection with the transmission of indications. Although it was energized, the circuits from (B+), and (B-) on its front and back contacts are not extended until after the operation of the first stepping relay. When stepping relay IV is picked up, relay FP is down and relay K drops before the circuit from (B+) on its front contact can be completed at front contact 'II of relay PP. The circuit through the back contact of relay K is ineffective to energize any of the PT relays during a cycle of this kind, since this circuit merely shunts the windings of these relays and does not complete a circuit for current flow. Relay K, after being released, does not pick up again during the transmission of controls.

The SOS relay is provided in order to improve the timing in connection with the operation of relay S0. The energizing circuit over control bus I53 for relay SO includes a winding of relay SOS and the operation of relay SOS completes a stick circuit for relay SO. Therefore, when this energizing circuit is interrupted by relay F restoring to normal, it would require the releasing time of two relays in sequence to drop the SO relay. The restoring of relay F to normal opens the circuit of relay FP and the stick circuit through back contact H3 of relay FP is therefore delayed slightly after the pick-up circuit of relay S0 is interrupted. By providing this additional relay, an overlap occurs which insures against the undesired release of the SO relay. Upon the next energization of the F relay the circuit for relay S0 is closed at contact I I8 before relay FP is picked up and back contact H3 is opened, which breaks the previously described stick circuit of relay SO.

Assuming that the last impulse applied to the line is of positive polarity, it is obvious that relay CS will be actuated over the circuit connected to its lower winding at the time the line is opened and the last stepping relay similar to 4V is picked up. Then when the line is closed by this positive impulse, relay CS is stuck up over a circuit extending from front contact I2 of the last stepping relay similar to 4V, front contact 66 of relay FP, front contact 61 of relay CS and its upper winding, to This stick circuit is also completed to at back contact 24 of relay SA in order that, under the above conditions, relay CS will not be deenergized but will remain stuck up after the first mentioned stick circuit through contact I2 is broken, at the end of the cycle. If relay CS should be released under these conditions, a false initiation of anothercycle might take place, due to momentarily opening the line 5, at its contacts I and 4. At the start of another cycle this stick circuit, through back contact 24,,

is broken so that relay CS will be down if the first impulse of the next cycle is Transmission of indications alone.Beforepro- 10 ceeding with the detailed operation of this feature of the invention, it will be mentioned that the SI relays are picked up at allstations ready to transmit new indications, at the initiation of an operating cycle. The system will go through a cycle 15 similar to'the one previously described and during thisv cycle the SI relays will be dropped out until only the one corresponding to the station having the superior code will remain. At those stations where the SI relays are released, the

2 stepping relay operation is discontinued and the operation of relays similar to FF is discontinued since their circuits are interrupted at front contacts I86 and I56 of relays similar to SI. 7

It will be noted that all SO relays are picked 5 up at the start of this cycle since their circuits are completed at contacts similar to -I II and H2 of relays SA and SAP. It will be recalled that when controls are transmitted, a preliminary impulse is appliedto the line before the first stepping relay is operated, which functions to maintain the SO relays in their operated positions during this portion of the cycle. When indications initiate the cycle, however, the first impulse is because no CD relay in the control office is picked up to completethe circuit for energizing relay CS. This impulse positions relay F1 to the left, picks up the FP relay and at this point there is no circuit for maintaining the SO relays and they are all dropped If an attempt is made to send controls over the system after indications start a cycle of operations, these controls will be stored and will be taken care of at the beginning of other cycles 5 in a manner fully disclosed in the above mentioned application, Ser. No. 455,304. The reason why it'is not possible to break into the cycle under this condition, is because a-relay CD can only be picked up at the normal period or the interval between cycles when the stepping relays are all released. 1

Referring to Fig. 2, it will be assumed that this station alone requires a transmission of indications and that some change in the condition 55 of a traffic controlling device or in the occupancy 60 to another.

65 ,as CI-IS, disclosed in the above mentioned patent, 1,852,402. station shown in Fig. 2 responds to an inbound code combination of (long, short, long), this being indicated by code jumpers I'Il, I12 and I13 for the first three steps respectively, being connected to indication buses I14 (long), I15 (short), and I14 (long), respectively. This station also causes the system to send the inbound code combination of (long,- short, long), due to 75 ,code jumper I8I preselecting a (long) fori the first It will also be assumed that the contact I62 of relay J and winding of relay PL to Relay PE .is operated over this circuit and closes a stick circuit for itself extending from its front contact I63, front contact I62 of relayJ and winding of relay PL to The operation of relay PL closes a circuit for operating relay vSI extending from back contact I64 of relay SAP front contact I65 of relay PL and upper winding of the SI relay, to

(). up under this condition, since relays similar to FL at other stations have not closed the pickup circuits of the SI relays at these stations, at front contacts similar to I65.

It having been assumed that the system was at normal when this condition was initiated, relays F and F will be in their energized positions and relay F? Will be in its normal or deenergizedposition.- This actuation of the PL relay opens, at its back contact I02, the normally closed and normally energized line circuit, which results in dropping the F and F relays, the latter starting the system through its I cycle of operations. Since this cycle will function in a manner similar to the one above described for controlling the control ofiice relays F, FP, SA and SAP, as well as the four stepping relays and the associated half step relay in the control office and since the F FP SA and SAP relays as well as the four a stepping relays and the half step relay at the station shown in Fig. 2, all function in a manner similar to that above described, this operation will not be explained again in detail. The start period is of long duration as before and the samesequence of operations is effected as above described for this period, except that relays CD and CS in the office are not picked up. Since Only the SI relay at this station is picked relay CS is not up during this cycle, all of the impulses applied to the line during its closed periods will be The same operations 'occur at the station as before, except that relay CH is down and relays PL and SI are up. Relay PL closes a stick circuit for relay SI extending from front contact I09 of relay SA front contact I66 of relay PL front contact I61 of relay SI and lower winding of relay SI, to During this start period the line is opened and relay J is released, which eifects the release of relay- PL -to close the line circuit at the station but the line is still open at the ofiice, because both the J and JP relays have not released in sequence within the time interval required to release J so that relay C is still up and it maintains relay PL energized, holding the line circuit open at its back contact 3. After relays PL and J at the station are released, relay SI is stuck are provided at field stations by selecting the length of time between impulses that are placed on the line at the control office. Sincethe first open period is used to start the cycle of operations and since this interval is a comparatively long one, it is evident that this first opening of the line circuit can not be used as a portion of the code combination.

The release of the PL relay at the station closes the line circuit, at its back contact I02, but the line is not energized until relay PL in the office is released to complete the closure of the line, at its back contact 3. This preliminary impulse period is effective to energize the J and JP relays in the ofiice and the J relay at the station by means of circuits previously described. Relay PL is actuated at this time over a circuit extending from code jumper I81, back contacts I68, I69, I88 and I89 of the four stepping relays in series, front contact I19 of relay SI, front contact I8I of relay FP front contact I6I of relay SAP front contact I62 of relay J and winding of relay PL to Relay PL establishes the above described stick circuit for itself, but at this time it does not open the line at its contact I02, because relay FP is picked up and its front contact I82 bridges back contact I02. Relay SI is stuck up at this time by way of front contact I66 of relay PL over the stick circuit previously described.

The line circuit is opened when relay PL, in the control office, is actuated during the preliminary impulse period. This open condition of the line circuit is the first indication code registration period and functions to pick up the first stepping relay IV, in the office and the first stepping relay 1V at the station. Relay PL at the station, having been actuated as above described, and since relay FP will be released during this open period, the dropping of relay PL in the ofiice fails to energize the line circuit by closing its back contact 3. It is open at contacts I02 and I82 of relays PL and FP respectively, at the station.

At the time relay PL in the oflice, in releasing, attempts to close the line and fails, it opens, at its front contact I8, the circuit of relay EB allowing this relay to release. A circuit is now established for picking up relay C, extending from front contact I5 of relay JP, back contact 68 of relay EB, contact 69 of relay Fand upper winding of relay C, to Relay C is stuck up by means of its stick circuit extending to the front contact I5 of relay JP. The picking up of relay C closes a circuit, at its front contact I1, which again picks up relay PL and it in turn closes a circuit, at its front contact I8, which operates relay EB.

Relays C, PL and EB are now held operated and the line is maintained in its open condition until sufficient time has elapsed to drop relays J and JP in sequence. During this time interval relay J 1 at the station will be released, and, at its front contact I62, the circuit of relay PL will be opened allowing this relay to drop but relay PL cannot energize the line circuit, at its back contact I02 at this time, because the circuit is open in the office. Relay SI is now stuck up over a circuit extending from front contact I09 of relay SA back contacts IIO, I16 and I11 of stepping relays 4V 3V and 2V in series, front contact I18 of relay IV code jumper I1I, indication bus I14, front contact I61 and lower winding of relay SI, to It will be understood that those stations which have a code combination with a long open period on this first step,

will be provided with code jumpers similar to [H and I81, the former being effective to hold the SI relays in their operated conditions at. those stations, and the latter being effective to make this period long. Also at those stations not supplied with code jumpers similar to HI and I81, when the period corresponding to the first step is long, there will be no circuit to maintain the SI relays and they will drop out.

When relay JP in the oflice releases, the release of relays C, PL and EB is effected and the next closure or energized period of the line occurs to pick up the F, FP, J, JP, E, PL and EB relays and to drop the VP relay in the control ofiice, all of which has been previously described in connection with this similar first control code registration period, during transmission of controls. During this closed condition of the line circuit as well as others which follow, relays F and PP at the station are picked up and relay VP is released. Relay J is also actuated and this relay as well as the J and JP relays in the oflice remain in their operated positions throughout the cycle until another long code impulse is required.

It was assumed that the second inbound code impulse is short, therefore, when the line circuit is opened for picking up the first stepping relays during the first indication code registration period, relay PL at the station is not operated, due to the fact that front contact I68 of relay IV and code jumper I9I are not connected to With relay PL down at the station and relay PL down in the office, the line is energized by battery B, and relay F opens its contact 69 before relay EB drops and closes its contact 68. Therefore, the circuit for picking up relay C is incomplete and the line will be immediately reenergized, thus resulting in a short open period for the second indication code. This energization of the line brings the system into the second control code registration period.

On this step, at stations having a code jumper similar to I12, the connection to on conductor I83 is extended through front contact I11 of relay 2V jumper I12 and through front contact I84 of relay J to the stick circuit of the SI relay. This maintains the SI relays in their operated positions at these stations, while at those stations not having this jumper, the stick circuits for the SI relays are incomplete and they are dropped out.

At the third indication code registration period, the line circuit will be held open for another long interval, since it was assumed that the final impulse of the station selecting code is a long one. This long open period is preselected at the time the 2V relay is operated, by Way of the circuit extending from code jumper I92, front contact I69 of this relay and over the remainder of the circuit previously described for picking up and sticking relay PL After the 3V and 3V relays are operated, the same sequence of operations takes place as above described for the previous long code and relay SI at the station shown in Fig. 2 is held by means of on conductor I83, being extended through front contact I16 of relay 3V code jumper I13, indication bus I14 and the previously described stick circuit of the SI relay. At the station or stations where this code jumper is not provided, the SI relays will be dropped out. The line will now be closed for the third control code registration period, after which it will be again opened to bring the system into the fourth indication code registration period.

If, at the time relay 3V was operated, an indication relay such as A had established a;circuit by way of its contact I85 to apply potential to the make contact I88 of relay 3V then relay PL would have been preconditioned to register another long open code signal during the fourth indication code period, or if there is no circuit completed at the make contact I88 of relay 3V for energizing relay PL then a short open code signal would be recorded. It will be obvious that other steps in addition to those shown may be arranged to select other indicating devices in rotation, similar to that indicated by reference character A Front contact I I of relay 4V (or the next succeeding stepping relay after the last station selecting step) holds the selected SI relay operated during indication selection and transmission. Thecircuit through the upper winding of relay CH of Fig. 2, extending from front contact I93 of relay SI, backcontact I94 of relay 4V and front contact I95 of relay 3V 'is for the purpose of restoring this relay, after station registration has been accomplished, following the release of the CH relay which started the cycle of operations.

If several stations have indications to be transmitted at one time, the PL relays at all of those stations will be picked up and the stepping relays at all such stations will start operating in synchronism. As will be later described in connection with the superiority of code operation, only one of the stations under this assumed condition will remain in connection with the circuit throughout the cycle. The stepping relays are not continued in operation at stations dropped out because their circuits are opened at contacts similar to I86 of the SI relays. Similarly, relays corresponding to FP at stations dropped out do not follow the impulses since their circuits are opened at contacts similar to I56 of the SI relays.

Since it has been described how the stepping relays in the control oifice and in the station are operated in synchronism during a cycle of operations, it will now be assumed that those in the control office are picked up one at a time and the registering of the station, as well as the registration of indications from the registered station, will be explained. During the periods when the line circuit is closed following the operation of each of the first three stepping relays, circuits are completed to relays P'l PT and PT respectively. These circuits extend from (B) or (B+) at the lower contacts of relay K, front contact II of relay FF and front contact of the operated stepping relay. In the case above assumed, the station having indication code (long, short, long) is registered.

During the first indication code registration period it may be assumed that relay IV is up. Relay K is picked up when relay JP is dropped 'by means of a circuit extending from back contact I5 of relay JP and lower winding of relay K, to When relay FP is picked up in the next or first control code registration period, it closes a stick circuit for relay K extending from front contact 32 of relay SAP, front contact 33 of relay FP, front contact 34 andupper. winding of relay K, to Relay FP also completes a. circuit for operating relay PT extending from (B+), resistance coil 14, front contact 12 of relay K, front contact H of relay FP, back contacts I8, 8| and 82 of stepping relays 4V, 3V:and 2V in series, front contact 83 of stepping relay IV and upper winding of relay PT to Relay PT is stuck up over a circuit including its lower winding, and its front contact I3 to at front contact 35 of relay SAP.

During the second indication code registration period relay FP is released, opening at its front contact 33, the stick circuit for relay K allowing this latter relay to release. Since this indication code is a short open period, relay JP will not be released at this time and K will not be picked up. Relay 2V is operated during this period and in the following period when relay FF is picked up the circuit from (B) through back contact 12 of relay K is ineffective to operaterelay PT since it merely shunts the winding of this latter relay. Relay PI is picked up on the closed period following the third indication code registration period, over a circuit extending from (B+), resistance coil I4, front contact 12 of relay K, front contact II of relay FP, back contact 18 of relay IV, front contact BI of relay 3V and upper winding of relay PT to Relay K is up at this time because the third indication code registration period is long which allows the JP relay to release.

During the fourth indication code registration period, relay ST is picked up and stuck up in multiple with relay 4V over the previously described circuit which operates 4V, which circuit is extended by Way of conductor 94, front contact 15 of relay PT back contact I6 of relay PT front contact H of relay PT and winding of relay ST, to Relay ST registers, in the control office, the selection of the station with an indication code combination which is (long, short, long). It will be apparent that other combinations of long and short open periods between im-' pulses may be used to pick up other combinations of the PT relays and that the operation of these relays will function to select other ST relays,

corresponding to other stations, when these additional ST relays are individually connected to the wires leading to bracket A. It maybe convenient to consider that a long code corresponds to a and a short code to a since the former is effective topick up relay K and it applies (3+) to the PT and the IN relays while a short code leaves relay K normal for applying (B-) to the pilot and indication relays PT and IN.

After the ST relay is picked up, additional indication codes are effective to position relay K which in turn positions the indication relays, such as IN, by connecting (3+) or (B) from the contacts'of relay K, by wayof front contacts II and I 8 of relays'FP and 4V respectively and front contact 19 of relay ST, through the winding of relay IN, to (ON) (CN) indicates an intermediate tap of the battery having terminals (B+) and (B) so that the position of relay K determines the positioning of relay IN.

The purpose of the stick circuit for relay K extending through front contacts SI and 92 of relays VP and 4V, is to guard against a possible false operation of an indicating device at the end of a cycle if relay K is up. Without this guard circuit, if K is up When SAP releases, relay K might drop away'before relay 4V and close a circuit through its back contact I2 for falsely positioningan indication relay similar to IN. With this guard circuit, relay K is held until either relay VP or:relay 4V is dropped after the release of relay SAP.

Superiority 0 code operation-Consideration has beengiven to the condition of only one field station transmitting new indications duringan operatingcycle. It will now be explained'how the system operates in the event thataplurality of field stations have new indications to transmit, during the same operating cycle. The fundamental requirement is that only one of said field stations can be registered in the control ofiice at a time under this condition and the method of accomplishing this result is similar to the method which is disclosed in detail in the previously mentioned application Ser. No. 455,304.

Those stations having their first code jumper I81 in condition for a long deenergized or open line period are superior to those stations which do not have this jumper completed to The reason why such stations are superior is because the line will be open for a long period by stations having an assigned coded arrangement requiring such long open period, in the same manner as if only one station was ready to send in new indications at the beginning of the cycle. This long open period will position the PL relay at the station having an inferior or short open period, so that the stick circuit of the SI relay will not be maintained. The SI relay is therefore down during the remainder of the cycle at the inferior station or stations, thereby preventing the operation being continued at those stations, because the circuit for conditioning the PL relay is broken at front contact similar to I19 of the SI relay.

The next open period in the line is coded by the remaining effective stations in the same manner, that is, if more than one station remains, due to the code jumpers similar to I81 being completed to at said stations, then during the period when relay IV connects the PL relay to code jumper I 9|, superior stations will have their circuits established for maintaining their SI relays, while inferior stations cause the release of the SI relays. Likewise when the 2V relay extends the circuit of relay PL to code jumper I92, since this is the last coding period of the cycle, only one SI relay will remain in its operated condition for completing station selectlon.

As an example, it may be assumed that two stations have new indications to transmit at the beginning of an operating cycle. It will be assumed that station No. 1 has an indication code (long, short, long) and that station No. 2 has an indication code (long, long, long). As above pointed out, station No. 2 is superior to station No. 1, since its code consists of all long periods. After the start of the cycle the PI. relays of both these stations are picked up because code jumper I81 is connected to at both stations. This condition causes the first indication code registration period to be long. The S1 relays at these two stations will be maintained in their operated positions when the PL and J relays at these stations release, because of the completed stick circuit for these SI relays by way of code jumper HI and indication bus I14.

During the second indication code registration period, relay PL at station No. 2 above assumed, is picked up since, at this station, code jumper I9I will be connected to but at station No. l the PL relay will not be picked up, since the code jumper corresponding to I9I is not connected to The picking up of a PL relay at a station at this time requires that the second indication code registration period be long. This is evident because any PL relay operating, opens the series line circuit which causes the control ofiice to apply a long open period.

The 2V relays are picked up during this period and at station No. 2 (with it long code) the' stick circuit for the SI relay is completed after the PL and J 1 relays are dropped, by way of code jumper I12 which is connected to indication bus I14 at this station. At station No. 1, code jumper I12 is connected to indication bus I15 so that there is no stick circuit for maintaining the SI relay in its operated position when relays PL and J are released. If two stations remain with their SI relays up at the third indication code registration period when relay 3V is picked up, then only one of these stations will continue, since there will be only one of those reaching this point which will have a jumper corresponding to I13 connected to indication bus I14.

Duplex operation.The manner in which the present disclosure operates to select one of a plurality of field stations and to transmit controls to the selected station when an operating cycle is manually initiated at the control office has been explained in detail. It has likewise been explained how the system operates to register one of a plurality of field stations in the control ofiice and to transmit indications from the registered station when the cycle is automatically initiated at the station. From the detailed description of the above operations, it will be clear that the selection of a particular field station and the transmission of controls to the selected station are accomplished by selecting the polarity or character of the energized line periods. It will also be clearly understood that the registration of a field station in the control office and the transmission of indications from such a field station are accomplished by the selection of the time intervals between the above mentioned impulses, corresponding to deenergized or open line periods,

Since such transmission of controls and indications take place during separate and distinct conditions of the line, these transmissions are independent of each other and may be incorporated in the same operating cycle when desired. Conditions requiring such simultaneous or two- Way transmission of controls and indications oc- 0111'" when controls are stored up at the control ofiice and new indications are stored at one or more field stations at the same time.

The operation of this system for accomplishing two-way or duplex transmission may be understood by assuming that a CD relay in the oflice and a CH relay at a station are conditioned at the start of an operating cyclerequiring transmission of controls and transmission of indications. It is obvious that a number of CH relays at a number of field stations may be positioned for transmitting new indications at the start of a cycle and that a number of controls may be stored in the control ofiice awaiting transmission.

In the case of a plurality of controls stored at l the control ofiice, it has already been pointed out that they are transmitted in an order determined by the arrangement of the CD relays, so that only one CD relay can be picked up at one time. It has likewise been explained how a plurality of field stations with new indications to be transmitted register themselves at the control office in rotation and in an order determined by the superiority of their code assignments. Since there are no complications involved in operating this system for duplex or two-way transmission, it is not believed necessary to describe the circuit operation during simultaneous transmission of controls and indications. The fact that transmission of controls and transmission of indications occur during the difierent periods of an operating cycle, as above outlined, indicates that these two transmissions may take place simultaneously, without interference complications.

When it is considered that the controls are transmitted by time spaced impulses of distinctive characters, with the particular control codes determined by reason of the distinctive polarity of the impulses, and that the determination of such polarity is entirely independent of the timing characteristic of the impulses, it is readily apparent that the timing may be varied in accordance with the indication codes to be transmitted from the field stations without in any way affecting the transmission of controls. In other words, the determination of the polarity of any impulses is entirely independent of the time spacing between successive impulses. Thus, the control oflice can selectively determine the polarity of the impulses simultaneously with the selective determination of the spacing between the impulses from the field stations.

As the operation of the system for the transmission of controls by the selective determination of the polarity of the control impulses has been explained in detail, as well as the selective determination of the time spacing between such impulses for the transmission of indications, and as these different conditions can occur simultaneously Without interference, the manner in which the simultaneous occurrence of control transmission and indication transmission may exist is believed to be entirely apparent to one skilled in the art. The operations involved are no different than the operations already described, when a particular station is receiving "controls simultaneous with its transmission of indications. The step-by-step mechanism at such a station is the only one which operates all the way through a particular operating cycle; but during a cycle of operation where one station is receiving controls and another station is transmitting indications, then both such stations have their step-by-step means operated throughout such a cycle of operation.

It will be seen that, when the system goes through an operating cycle, for transmission of controls, a preliminary impulse is applied to the line before the code impulses are sent. This makes it possible to use all eight code combinations obtained with three steps, without the provision of special circuit arrangements to care for the condition when indications alone are transmitted. When only indications are being trans-. mitted the line is energized with a series of impulses, including the preliminary impulses, which will not be effective to maintain any SO relay energized throughout the series, because without a preliminary they Will all be dropped out. Therefore, no special circuit arrangenients are required to repeat controls to a station having a code combination of because, even though a station uses this code it will not be selected by an indication cycle of This is due to the fact that such a cycle has a preliminary A preliminary is required to make this code effective.

On the other hand, when controls alone are being transmitted, the same condition for station registration exists as if new indications were being transmitted, that is, the system will send an inbound codecombination of and impulses equally spaced which is code (short, short, short). If this code were effective to select a ST relay under this condition, false indications-would. result due to the fact that noSI tions to relay K after station registration.

There are two ways of handling this condition; first, not use this inbound code by not connecting wire 81 of Fig. l .to a ST relay; second, assign thiscode to a station, connect a jumper Wire across terminals X and Y at this station (see Fig. 2) and connect a station relay to wire 81 of Fig. 1. With this arrangement, at the start of each cycle, even if it is for the transmission of controls alone, relay SI at this station will pick up. The pick-up circuit is effective after relay SA picks up and before relay SAP picks up and extends from back contact I64 of relay SAP front contact 264 of relay SA jumper connection KY and upper winding of relay SI, to Of course, only the SI relay at the station with code (short, short, short) will be up after station registration and its corresponding ST relay at the oflice will be operated. The circuit will then function to transmit indications from this station (even though they are not new ones) to the control ofiice and they will be as correctly recorded as if a series of new indications were transmitted.

Recheck.-A recheck feature has been provided in this system for the purpose of enabling the operator, in the control oifice, to put the apparatus through an additional cycle of operations, after indications have been transmitted. There may be some doubt in the operators mind as to a certain indication being properly displayed. In this event it is only necessary for him to operate a starting button, which will pick up a CD relay and cause the system to go through a cycle of operations, The S0 relay, corresponding to the station selected by the starting button, will be picked up at the station in question and at the .end of the cycle, before relay S0 is dropped, a

circuit is closed for operating indication recheck relay IR, extending from back contact I09 of relay SA front contact I of relay SAP front contact I96 of-relay SO, back contact I91 of relay SI, front contact I98 of relay CH and winding of relay IR, to This circuit is effective at the end of the cycle when relay SA is released and before the release of relays SAP and S0. The operation of relay IR establishes a stick circuit for itself including its front contact I 99. Relay IR closes a circuit, at its front contact 2M, for energizing thermal relay IRP. Relay IR likewise removes at its back contact 202, from the lower winding of the CH relay, but this latter relay does not release at this time, due to a branch circuit to including contact 203 of the thermal relay. After the necessary time interval required for heatingthis relay, its contact 2833 is broken and relay CH is deenergized. This is effective to close back contact I58, which will put the system through an additional cycle of operations in the manner above described for registering this station in the control oifice and displaying the required indications.

It will be noted that this same circuit is effective to pick up and stick relay IR on each cycle used for the transmission of controls. On such cycles, however, some relay, such as WP, will be shifted, resulting in the dropping of relay CH, which opens, at its back contact I98, the circuit of relay IR. New indications are transmitted, due to the shifting of a relay such as WP and, shortly after the release of relay CH, relay IR is dropped.

The recheck feature, above described, enables the operator to initiate a cycle of. ope-rations for transmitting indications from a desired station, Without transmitting new controls to such a station.

Operation of modification.-A modification of the station circuits is shown in Fig. 3, which is an arrangement for selecting groups of indications at the same station, without the necessity of providing groups of complete relay equipments. One complete set of relays is provided at the station for controlling most of the circuit operations. The SI relay functions to select the station and it, as well as the stepping relays and other relays shown in Fig. 2, are common to all groups at the same station. It will be understood that group No. 1, indicated in Fig. 3, has a complement of relays as shown in Fig. 2, with the added LC and LCS relays. Group No. 2 and other groups at this same station have only their LC and CH and indication relays such as A The wires leading off to the right of the drawings are common to the station and connect to relays, such as LC, A of additional groups, at points corresponding to those indicated associated with group No. 2. Code jumpers 264, 265 and 266 are variably connected at group No. 1 to properly code the time intervals between impulses during transmission of indications, for marking this group for selection. Code jumpers 26I, 262 and 263 are variably connected to control the station selecting relay SI. Corresponding code jumpers 214, 215 and 216 at group No. 2 are likewise variably connected to properly code the impulse periods for marking group No. 2 for selection. Likewise, code jumpers 21I, 212 and 213 are variably connected to control the station selecting relay SI.

It is believed that the operation of this modification will be best understood by describing briefiy the operation when indications are to be transmitted from group No. l and from group No. 2. It will be assumed that group No. 1 has an inbound code combination (long, long, short), as indicated by code jumpers 266 and 265 being connected to They preselect the first and second indication code registration periods, respectively. Jumper 264 is omitted so that a short indication code registration period is preselected for the third period. This code combination is likewise indicated by code jumpers 263 and 262 being connected to indication bus I14 for sticking the SI relay during the first and second indication code registration periods, respectively.

Group No. 2 is assigned an inbound code (long, long, long). This is indicated by code jumpers 216, 215 and 214 being connected to It will be understood that these code jumpers preselect the time intervals between impulses for the first, second and third indication code registration periods and since they all are connected to potential, all these periods will be long. Code jumpers 213, 212 and 21I are connected to indication bus I14 so that the SI relay will be stuck up during the first three indication coderegistration periods.

It will thus be seen that the code jumper arrangement departs from the scheme disclosed in connection with Fig. 2, in that these jumpers are not directly selected by the stepping relays but the stepping relays select common wires leading to contacts of all LC relays of a station and the particular LC relay which is picked up extends these common wires to the code jumper connections. In this way a station is selected by making the SI relay responsive to a number of code combinations and the indication devices such as A and A are selected after the selection of the station is completed, by means of the particular LC relay which is energized.

CH and CH are the change relays normally energized and released when a change in indication occurs which requires transmission to the control office. LC and LC are the interlocking control relays and are for the purpose of permitting only one group at a station to be selected at one time. The operation of these LC relays is by means of a series circuit through contacts of corresponding CH relays, with a cooperating LCS relay which operates and opens the pick-up circuit of the LC relays as long as one of the latter is. stuck up.

Assuming that group No. 1 has new indications to be transmitted and that the CH relay is released, in a manner previously explained in connection with Fig. 2, then at the start of the cycle, a circuit is closed for picking up relay LC extending from back contact 25I of relay SA back contact 252 of relay SAP back contact 253 of relay LCS, back contact 254 of relay CH and upper winding of relay LC to Relay LC is stuck up over a circuit extending from back contact 251 of relay 4V in multiple with a circuit to at back contact 255 of relay SI, winding of relay LCS, front contact 256 of relay LC and lower winding of this relay to Relay LCS operates and opens the pick-up circuit of all LC relays, so that another LC relay can not be energized until the end of this cycle. This stick circuit is effective until relay 4V is picked up to disconnect at its back contact 251 and until relay SI is picked up to disconnect at its back contact 255. The purpose of the stick circuit through contact 255 is to maintain a LC relay stuck up even after relay 4V is operated at the end of a cycle, in the event that the cycle is used for transmitting controls. This holds over an operated LC relay until the start of another cycle, if it is picked up during a control cycle. The operation of relay LC closes a circuit, at its front contact 258, which is effective to pick up the CH relay which was released to initiate this cycle, the circuit extending through contacts I94 and I95 of relays 4V and 3V which circuit was previously described.

Relay LC extends the connection from through code jumper 266, by way of its front contact 259, to the back contact I68 of relay IV and thence by Way of the remainder of the previously described circuit to conductor 205, which is effective to pick up relay PL for preselecting a long code interval on the first step. Likewise, front contact 261 of relay LC connects through code jumper 265 over this same circuit for preselecting a long time interval for the second step. Contact 268 connects to jumper terminal 264, but since there is no jumper at this point, a short time interval is preselected for the third step.

Front contact 269 ofv relay LC extends the stick circuit of relay SI, connected to indication bus I14, by way of code jumper 263 and front contact I18 of relay IV to conductor I83, which is connected to at front contact I69 of relay SA This circuit is effective to stick the SI relay at the first step. Front contact 211 of relay LC connects jumper 262 to the above described circuit for sticking the SI relay on the second step. Front contact 218 connects jumper 26I to indication bus I15 for sticking the SI relay, over the above described circuit, at the third step.

Group No. 2, with an inbound code combination (long, long, long), has its preselecting jumpers 216, 215 and 214 all connected to so that they are effective to respectively preselect long time intervals for the first three code periods. These jumpers are connected to the common conductors leading to contacts of the stepping relays, by means of front contacts I, 282 and 283 of relay L0 Code jumpers 213, 212 and 21| are all connected to indication bus I14, so that the SI relay will be held by the three long time intervals. These jumpers are connected to the common wires, by way of front contacts 284, 285 and 286 of the LC relay.

After the particular group of the station is selected, indications are transmitted by means of the long and short time intervals, in a manner previously described in connection with the operation of Fig. 2. Front contact I88 of relay 3V connects conductor 205 leading to relay PL by way of front contact 219 of relay LC to register indications due to the energized or deenergized conditions of relays such as A If group No. 2 is selected, relay LC is picked up and the above mentioned indication circuit is extended by Way of front contact 281 of relay L0 to contacts of indication relays, such as A associated with group No. 2. It will be understood that relays LC and LC are supplied with additional contacts similar to 219 and 281 for connecting other indicating devices, similar to relays A and A during additional steps to conductor 205, for sending additional indications to the control office.

It will thus be seen that two or more code combinations are used for selecting the same SI relay to select a desired station. After the station is selected only one LC relay at the selected station will be picked up, therefore, indications from the selected group at this station will be transmitted. This provides selection of stations by means of the SI relay, selection of groups by means of the LC relay and transmission of indications from the selected group, through the contacts of the selected LC relay.

It will be understood that when an arrangement of this kind is used there will be a relay ST in the control ofiice for each group relay LC at the station, rather than one ST relay for each SI relay, as disclosed in connection with Figs. 1 and 2. It will also be understood that a plurality of stations may be provided with a plurality of groups at each location, operating in the manner explained in connection with Fig. 3 and that duplex operation will be efiected, as well as superiority of code, in a manner described in connection with Figs. 1 and 2.

The above rather specific description of the invention is given solely by way of example and is not intended in any manner whatsoever to be in a limiting sense. Obviously, the invention can assume various different physical forms and is susceptible of numerous modifications and all such forms and modifications as come within the scope of the appended claims, are intended to be included within the scope of the invention.

Having described my invention, I now claim:

1. In a centralized traflic controlling system, a control office, a plurality of field stations, a line circuit extending from said control oflice to said field stations, step-by-step means at said control oifice and at said field stations responsive to impulses applied to said line circuit, means for applying a plurality of variably time spaced impulses of distinctive character to said line circuit for operating said step-by-step means at said control office and at said stations in synline circuit extending from said control ofiice to said field stations, step-by-step means at said control oflice and at said field stations responsive to impulses applied to said line circuit, means for applying a plurality of variably time spaced impulses of distinctive character to said line circuit during an operating cycle for operating said step-by-step means at said control ofilce and at said stations in synchronism, means responsive to the character of said impulses on successive steps for selecting a first one of said stations to receive controls from said control ofiice, means responsive to the variations in time between said impulses for the successive steps for selecting a second one of said stations to transmit indica tions to said control ofiice, and means for continuing the operation of said step-by-step means throughout said cycle at only said first and said second stations.

3. In a centralized traflic controlling system, a control ofiice, a plurality of field stations, a line circuit extending from said control office to said field stations, step-by-step means at said control office and at said field stations responsive to impulses applied to said line circuit, signaling devices at said control oflice and at said field stations, means for applying a plurality of variably time spaced impulses of distinctive character to said line circuit for operating said stepby-step means at said control office and at said stations in synchronism through an operating cycle, means responsive to the character of said impulses for selecting one of said stations and for operating said signaling devices at the selected station during the steps of saidv operating cycle, and means responsive to the variations in time between said impulses for the steps of said cycle for identifying in the control office another of said stations and for operating said signaling devices in said control oflice during the steps of said operating cycle.

4. In a centralized traific controlling system,

a control oflice, a plurality of field stations, a line circuit extending from said control ofiice to said field stations, step-by-step means at said control office and at said field stations responsive to impulses applied to said line circuit, signaling devices at said field stations, indicating devices at said control oifice, means for applying a. plurality of variably time spaced impulses of distinctive character to said line circuit for operating said step-by-step means at saidcontrol office and at said stations in synchronism through an operating cycle, means responsive to the distinctive character of said impulses for selecting one of said stations and for operating its associated signalling devices thereat on the respective steps during said operating cycle, and means responsive to the variations intime between said impulses for registering'said one of said stations and for operating its associated indicating. de-' vices in said control ofiice on the respective steps during said operating cycle.

5. In a centralized traffic controlling system, a control ofiice, a plurality of field stations, a line circuit extending from said control oflice to said field stations, step-by-step means at said control office and at said field stations operated in synchronism by impulses applied to said line circuit, impulsing means at said control ofi'ice for applying a series of impulses to said line circuit and for variably spacing the time intervals between said impulses to form a code combination, means controlled by said code combination through the medum of said step-b-ystep.;means for selecting one of said stations, means at said station for preselecting said code combination and causing such preselected code combination to be formed by said impulsing means, and means controlled by said code combination for registering said selected station in said control office.

6. 'In a centralized traffic controlling system, a control ofiice, a field station, a line circuit extending from said control ofiice to said field station, impulsing means at said control oilice for applying a series of time spaced impulses on said line circuit, step-by-step means at said control office and at said field station operated in synchronism in response to said series of impulses applied to said line circuit, means at said station for opening and closing said line circuit on certain steps of said step-by-step means to form a code, means at said control office responsive to said opening and closing of said line circuit at said field station for causing said impulsing means to provide long and short time intervals respectively between said impulses to form said code combination, and means at said station distinctively responsive to said code combination.

'7. In a centralized trafiic controlling system, a control oflice, a plurality of field stations, a line circuit extending from said control ofiice to said field stations, step-by-step mechanism at said control office and at said field stations responsive to impulses applied to said line circuit, impulsing means at said control ofiice for applying a series of impulses to said line circuit during an operating cycle for advancing said mechanism in synchronism, code means at said control office for causing said impulsing means to provide long and short time intervals between said impulses to form difierent code combinations, means controlled at a first one of said stations for determing that a code combination for selecting said first station be caused by said code means during said operating cycle of said step-by-step mechanism, and means controlled at a second one of said stations for changing the control of said first station over said code means so that a code combination is caused which will select said second station in preference to said first station during said operating cycle.

8. In a centralized trafiic controlling system, a control office, a first field station, a second field station, a line circuit connecting the control ofiice with the field stations, step-by-step mechanism at the control ofiice and at the stations responsive to impulses on said line circuit, means at the control ofiice for applying a series of impulses to the line circuit to comprise an operating cycle for advancing said mechanism step by step in synchronism, station selecting means at the stations initially conditioned for operation at the start of said cycle, means controlled by said first field station for opening the line circuit duringcertain steps of said mechanisms, and means in the control oflice responsive to the opening of the line circuit by said first station for continuing the operation of the station selecting means at said first station and disabling the operation of the station selecting means at said second station.

' 9. In a centralized traffic controlling system, a control ofiice, a first field station, a second field station, a line circuit connecting said control ofiice with said field stations, step-by-step mechanism at the control oifice and at the stations responsive to impulses on said line circuit, means at the control ofiice for applying a series of time spaced impulses to the line circuit during an operating cycle for advancing said mechanisms step by step in synchronism, station selecting means at the stations initially operated at the start of said cycle, means controlled by said first field station for momentarily opening the line circuit during certain predetermined steps of said mechanisms, means in the control ofiice responsive to said momentary openings for extending the time interval between associated impulses for the corresponding steps, and means responsive to said extension of certain time intervals for continuing the operation of the station selecting means at said first field station and disabling the operation of the station selecting means at said second station.

10. In a centralized traffic controlling system, a control office, a plurality of field stations, a line circuit extending from the control ofiice to the field stations, means at the control ofiice for applying a series of impulses to the line circuit to comprise an operating cycle, timing means at the control ofiice for providing long and short time intervals between impulses to form code combinations, a starting relay in the control oflice manually controllable in the control ofiice and automatically controllable over said line circuit from said field stations for initiating said operating cycle, means at said stations for conditioning said line circuit to determine the short and long duration of said time intervals as applied by said timing means to form a particular code, means at the control office for registering said particular code, and means at said field station controlled by said code combination for selecting a particular one of said field stations.

11. In a centralized traffic controlling system, a control ofiice, a field station, a normally closed line circuit extending from the control office to the field station, means at the control office for opening and closing the line circuit to form a series of time spaced impulses, step-by-step mechanism at the control office and at the field pulses, code selecting means at the field station rendered successively effective by said stepping mechanism to predetermine the normal or abnormal time space between successive impulses, and means at the control ofiice responsive to said code selecting means for changing a normal to an abnormal time space.

12. In a centralized trafiic controlling system for railroads, a control ofiice, a plurality of field stations, a communicating circuit extending from the control ofiice through the several field stations, means in the control ofiice for applying impulses of current to said communicating circuit at uniformly time-spaced intervals, stepping relays at the control ofiice and at each station operated sequentially by said impulses, means at each station efiective to selectively extend the time-space between said communicating circuit impulses, and means at the control o-flice respon- 2.55 station operated in synchronism by said im- 

